Abstract
Overwintering site of the bean bug, Riptortus clavatus, was evaluated from a choice test in a cage from December 2003 to March 2004. To test which environmental conditions were preferred as an overwintering site, four cages were placed in the field. In each field cage, four types of substrate made of rock, a young tree of Japanese cedar with fallen leaves of Japanese cedar, dead grass weed, or fallen broad leaves were set up. The adults of the bean bug were maintained in the laboratory at 25°C, 10L14D for induction of diapause. In mid December 2003, 193 adult bugs were released in each field cage and adults in the cages were collected March 2004. Numbers of collected bugs differed significantly among the four conditions (Japanese cedar>dead grass weed>fallen broad leaves>rock), suggesting that this species preferred Japanese cedar forest and grass weed as overwintering sites.
